The present invention relates to reciprocating closure valves, especially for use in pumps which pump fluids containing entrained solids.
Fluid pumps are conventional which, as depicted schematically in FIG. 6, employ a reciprocating piston 1 or the like to suck fluid past a reciprocable inlet valve 2 and into a chamber 3 during a suction stroke, and then force the fluid through a valved discharge port 4 during a discharge stroke. The inlet valve 2 is mounted for reciprocation and is biased by a spring 5 to a closed position against a rigid seat 6. The inlet valve 2 is pulled open by a low pressure produced in the chamber 3 during a retraction stroke of the pump piston, and thereafter is pushed closed by a combination of the spring force and high pressure produced in the chamber 3 during an extension stroke of the pump piston. When the inlet valve closes, the high pressure fluid within the chamber 3 is pushed out through the discharge port 4 which itself contains a spring-biased valve 7.
The inlet valve 2 typically comprises a metal body 8 on which an annular elastomeric seal element 9 is mounted to make contact with the seat 6. The mounting of the seal element may require the provision of retaining plates or the like which must be detached and reattached in order to enable worn seal elements to be replaced. The presence of such retaining plates increases the initial valve cost and complicates the replacement of worn seal elements. The latter shortcoming is of particular concern when the fluid being pumped contains solids (e.g., dirt, gravel, tree parts, etc.) which accelerate the wear of the seal element. Since the pump is inoperative during replacement of the seal element, it will be appreciated that enhanced pump efficiency would be realized if the time for replacing a seal element could be reduced, and if the life span of the seal element could be increased.